Listmonk was posted here some time ago, I have yet to try it out, but if you are not scared by alpha-quality code, it could be a good free performance-driven alternative to this: https://github.com/knadh/listmonk
Not intentionally picking on Listmonk (or you), but when I hear "alpha-quality code" and start thinking about the complexities of marketing emails with GDPR, CCPA, and the constant threat of blacklists and otherwise getting blocked by big G, I run for the hills.
